Fakarava atoll, French Polynesia
work done in 2014-2016



Operational 2K: problem solved


 
1 - NO NEED for field data, nor for atmospheric correction
2 - this is demonstrated in this website, using a variety of hyper/multi spectral data
 
Requirements are
1 - homogeneous water body and atmosphere
2 - some coverage of optically deep water
3 - some coverage of dry land
 
Problems are
1 - the precision on estimated depth is found wanting, because the noise-equivalent change in radiance  of accessible data is too high for shallow water column correction work 
2 - radiance data should be preprocessed by the provider at level 1 in order to improve S/N ratio
3 - exponential decay: the deeper/darker the bottom, the poorer the performances
 
So
I keep digging
until suitable data
become available
 


 


OLIP 25_july_2014
TCC
Fakarava is the largest atoll

Other atolls are
Aratika, Kauehi, Raraka, Faaite and Tahanea,
each with its own special water optical properties,
which must be assessed and operated separately

Calibration for bands 5_4_3_2
band 4 contains the PAN channel

This calibration only accounts for
the clearest waters inside all lagoons,
excluding open waters

 
  • Clearest      is Kblue/Kgreen=0.47 at  Toau
  • Least clear is  Kblue/Kgreen=0.65 at  Kauehi

 



Bad fit
WL
RED  at mid-waveband
for the optical calibration
yields a bad fit


WLred mid-waveband at 655 nm
Notice the flawed fit



Good fit

 Shifting WLRED
for the optical calibration
yields a good fit



WLred shifted at 615 nm
Notice the good fit
  • WLred is decreased from 655 nm to 615 nm
  • it should suffice to decrease KRED as appropriate
 


OLIP 22_mars_2015

Coastal band, deglinted
Note the negative contrast
at Tahanea, Raraka, Kauehi, and Taiaro

Blue band, deglinted
Note the negative contrast
at Tahanea, Raraka, Kauehi, and Taiaro

good fit : coefK=1.0
Landsat 8 OLI 22 march 2015







good fit : coefK=1.0
Landsat 8 OLI 22 march 2015